Process of spinning hollow articles



iNVENTOR CHARLE J. URCH Auxiliary name C. J. BURCH PROCESS OF SPINNINGHOLLOW ARTICLES Flled June 10, 1943 Patented Aug. 20, 1946 PROCESS OFSPINNING HOLLOW ARTICLES Charles J. Burch, Plainfield, N. J assignor toThe Linde Air Products Company, a corporation of Ohio Application June10, 1943, Serial No. 490,295

2 Claims.

This invention relates to the art of metal working and more particularlyto spinning end closures in hollow articles.

In spining the open end portion of a, metal tube or cylinder, the end ofthe blank is closed at the center. The central portion of the closure,however, is non-homogeneous, being traversed by a hair-line pipe orvalley, which is highly undesirable especially in chemical bombs and thelike. To overcome this in the past it has been proposed to drill out thedefective central portion of the spun closure and fill the resultinghole with a plug. It has also been proposed, in the case of brass parts,to put a drop of'solder on the formed closure as a precaution againstleaks. Such proposals involve additional material and added steps inmaking the finished product and are not entirely satisfactory inavoiding leaks in the case of gas containers in which the gas is under aminimum pressure of the order of 100 pounds per square inch, forexample.

Therefore, themain object of thi invention is to provide an improvedspinning process of closing the open end of a metal cylinder or tube,which overcomes difficulties and disadvantages of the prior art andresults in an end closure that is entirely free of oxide inclusions andis homogeneous throughout. Another object of the invention is to providea tube end closure spin ning process which eliminates the hair-line pipefrom the resulting end wall. A further object of the invention is toprovide an improved product.

In a hot spinning operation where the tube end is to be closed, it hasbeen the practice to heat such end prior to, or during forming, to atemperature that would allow the metal to be easily spun inwardly. Thecenter of the end closure would thus be formed shut, and a forge weldsimulated. However, the formation of oxide on the metal surface thusforced together, led to oxide inclusions and a doubtful closure at theend. According to the present invention, by means of an auxiliary flame,directed at the center'of the end just as the edge is being forcedclosed, a true fusion weld is made, thus assuring that the oxides willbe melted and forced out, and solid metal result.

More particularly, according to the present invention, there i providedthe process of forming hollow articles, which comprises closing the openend of a metal cylinder by a spinning operation, the final closure beingincidentally subject to a hair-line of oxide inclusions, and preventingsuch hair-line by directing a high-temperature flame against the work soas to melt the metal in the closure immediately prior to the completionof the spinning operation, and extruding the melted meta1 and all oxideinclusions from the resulting closure, so that the metal is homogeneousthroughout.

Referring to the drawing:

Fig. l is a fragmentary view partly in cross section and partly in sideelevation of a rotating tube having its end portion heated by th flamesof a multiflame heating head;

Fig. 2 is a similar view of the tube at the beginning of the spinningoperation, an auxiliary flame being directed against the work so as tomelt the metal at the zone of closure;

Fig. 3 is a similar view showing the auxiliary flame directed againstthe work at the zone of closure during the completion of the spinningoperation;

Fig. 4 is a similar view of the completed closure without oxideinclusions;

Fig. 5 is a fragmentary view in cross section of a cylinder having asemi-spherical end closure made according to the invention;

Fig. 6 is a similar view with the auxiliary flame directed against theinside of the closure; and

. Fig. 7 is a similar view of the resulting closure which is entirelyfree of oxide inclusions.

Referring to Figs. 1,. 2, 3 and 4 of the drawing, the end portion Ill ofa tube or cylinder C is heated by the group of flames ll extendinglongitudinally of the end portion In and directed perpendicularlyagainst the same from a multiflame heating head H which is mounted inproper lateral position with respect to the tube C, the latter beingrotated about its longitudinal axis by any suitable machine (not shown).The flames ll are preferably produced by burning amixture of oxygen andacetylene which may be mixed either externally or internally of the headH. Post-mixed oxy-acetylene flames are preferred as the heating means,although the end portion It of the tube C may be heated in a furnace orby induction or in any suitableway including friction. After the endportion ID of the tube C has been suitably heated, a tool T appliespressure inwardly against such heated portion lfl as the tube C rotatesabout its longitudinal axis, and the heated portion i9 is spun or turnedinwardly, as shown by Fig. 2. In order to prevent hair-line cracks oroxide occlusions at the center of the resulting closure, according tothe invention, an auxiliary flame l2, preferably an oxyacetylene flamefrom a blowpipe 3 l nozzle N, is directed against the extreme annularend !3 of the rotating workfi.

As the spinning operationjcontinues, as shown by Fig. 3, the.auxiliaryfianie i2 is kept directed against the edge ['3 of the tube C,so that a puddle or appreciable amount M of molten metal formedatthecenter of the closure. .As the closing operations is. completed,some of the melted metal and all of the oxide inclusions are axiallydisplaced, leavin an end wall 15 the interior of which i entirely freeof oxide inclusions, the metal being solid and homogeneous throughoutsuch interior. I

By way of example, a tube (Lhaving an outside diameter of 1.35 inches,anda wall thickness of 16 gauge, was heated by the multiflameoxy-acetylene heating head I-Land a scmare end closure l5 formed by theflat faced tool TV While,

the end was being closed, a single auxiliary flame i2, burning about 9cubic feet per hour of oxygen and a like amount of acetylene; wasdirected manually at the point of the closing cone just. before it wascompletely closed. A true fusionweldthusrwas produced at the center oftheclbsure, which closure was gas tight under 100 pounds per square inchof" hydrogen.

Hair-line cracks or oxide inclusions at the center'and all doubts as towhether the tubes are perfectly sealed'are 'eliminatedby-the use of anauxiliary flame according to the present invention.

In,.the' example given above, a No. 6 tip attached to a W'17. oxweldblowpipe was used to obtain the auxiliary flame l2. After the mainheating head H was shut ofi, the forming operation was started. Theauxiliary-flame l2 was direotedagainst'the,edge |3*of thetube C in asubstantially axial direction; As the forming progressed, this edge itmoved toward-the center somewhat like ashutter, decreasing the diameterof the opening at the smaller end of the conical portion. When suchdiameter reached inch to inch, the edge l3 was visibly molten and rantogether forming a puddle M at the center. Thus, while the end portionwas still in the form of a cone, the end orthe tube wasperfectly-'sea'led Further forming pushed in the cone, leavin'g a flatend and a substantially square annular corner 16.

Referring toFig. 5,.the.open'end of a metal cylinder. D is shown.beingzclosed by a hot spinningLO er-ation. Oxide inclusions in the finalclosure: are :entirely prevented,according to the invention jbydirecting the-flame 12 against the worked as to melt the metal; at H inthe closure I 8,-immediately prior-to the completion of the hot spinningoperation which closes'the end wall IQ of. the cylinder D, as shown byFig. 7. In this example, the end wall I9 of the cylinder issemispherical, and is entirely free of oxide inclusions, the metal beingsolidandhomogeneous throughout.

Fig. 6 shows a modification 'wherein the flame [2 is directedcontinuously against the work E at the zone 28 of closure from theinside of the cylinder E, during the completion of the hot spinningoperation to eliminate oxide inclusions entirely from the closed end 2|of the cylinder. The. resulting product is like that shown in Fig.7.

A featured the invention is the actual melting of the metal at the edgebefore the opening .is completely closed, to form a real fusion weld,

as distinguished from a simulated forge weld of the prior art inwhichthe metal is said to weld itself together at the line or point ofclosure. The latterproduces an inferior weld that includes objectionableoxides which are eliminated by the present invention.

ln the m'odifica'tion of the invention shown in Fig. 6, it will beunderstood that the internally disposed auxiliary flame l2 may bedirected against the end closure in accordance with the invention whileaforming tool is being applied to the outside of the semi-spherical endportion of the tube or cylinder E.

Practice of the present invention entirely eliminates the hair-linecrack or oxide inclusions which'was present in all closures formed byspinning operations known prior tothe invention. Thus, the inventionreduces the cost and improves the resulting product to such an extentthat it has gone into commercialuse on a large scale in the manufactureof chemical I bomb burster tubes and the like.

What is claimed is:

l. A method of closing an end of a tubular metal article which comprisesrotating said article about its longitudinal axis while initiallyapplying a group of heating flames longitudinally to a portion of thearticle extending back from the open end to be closed; applying pressureinwardly against such heated end portion while the article is rotating,to spin inwardly said heated portion and the periphery of its end edgeand thereby progressively close said end of said article; and, beforesaid end is completely closed and while continuing such rotation andsuch application of inward pressure, directing an auxiliary flame,separate from said group of flames, against said end ecEe-and the partadjacent thereto, to provide suilicient additional heat to melt metalalong said edge at the final closing zone, whereby oxide inclusion iseliminated from said'closing zone as said end is completely closedduring the continuance of such rotation and such application of inwardpressure.

2.1A method of closing an endiof a tubular metal article as claimed inclaim 1, wherein said auxiliary flame is disposed within said tubularmetal article and is directed against the interior side of said end edgeand the interior surface of the part adjacent tozsaid edge.

CHARLES J. BURCH.

